Vehicle engines may be configured to operate on various fuel blends. Such vehicles, sometimes referred to as flex-fuel vehicles, may be configured to operate on gasoline, for example, with varying levels of ethanol, ranging from pure gasoline to E85 (85% ethanol and 15% gasoline).
However, the inventor herein has recognized a problem with engine degradation in vehicles operating consistently on higher alcohol fuels, such as E85. Specifically, engine main bearing fatigue has been observed during high speed durability testing while running with 85% ethanol blends, whereas the same engines have no bearing fatigue when running with gasoline only and tested at the same engine speeds. While it may be possible to change main bearing material to address this wear issue, this can increase manufacturing complexity and increase cost. Likewise, it may also be possible to change the recommended engine oil to address the wear issue, but such a change may decrease the vehicle fuel economy.
As such, in one approach, the above issue may be at least partially addressed by limiting the engine speed to a maximum permitted engine speed during vehicle operation responsive to the amount of alcohol.
In this way, it is possible to maintain common main bearing designs among gasoline and flex-fuel engine designs, maintain fuel economy, and further it is possible to address cost and manufacturing complexity while also accommodating various fuel types. However, it is also possible to apply the above approach in combination with changes to the main bearing material as well as changes to the recommended engine oil, if desired.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.